I'd go for Spiked Battleguard.
Collar has 97 AP, non-scaling. After Kings and Improved Zerker, Spiked Battleguard gives 171 AP. As well, the hit on Battleguard is going to help rage gen a lot. You lose 10 crit rating and a little bit more crit chance from agility, but your unbuffed crit doesn't look bad anyways.
That said, I don't know exactly how much crit chance you'd be losing, nor can I accurately place a value on the ArP, but you seem to have a lot, so maybe it would be worthwhile. You'd have to ask a better theorycrafter.